This invention relates to a method for generating record data and, more particularly, to a method for generating record data by encoding a main information consistent with various specifications or formats, such as those for digital audio, CD-ROM or CD-I, as prescribed on the basis of the standards for a so-called compact disc (CD).
A variety of specifications or formats, such as those for CD-ROM (compact disc-read only memory), or CD-I (compact disc-interactive), for example, are prescribed in compliance with standards for existing recording media, such as compact discs (CDs). It is in conformity to these specifications or formats that data of various specifications or formats, such as the aforementioned CD-ROM data or CD-I data, are recorded, in place of the usual digital audio data, as the main data or information which is to be recorded in compliance with the standards for the recording media, such as CDs. This allows the existing media to be used more flexibly and extensively.
FIG. 1 shows a frame format and a block format consistent with the so-called CD standards. In this figure, each block or sector consists of 98 frames of from the 1st to 98th frames, each frame being 588 times a channel clock period T or 588T and consisting of a 24T frame sync pattern part plus 3T connecting bits, a 14T sub-code part plus 3T connective bits and a 544T data part composed of audio data and parity data. The 544T data part is the EFM data (eight-to-fourteen modulated data) consisting of 12 bytes or symbols of audio data, 4 bytes or symbols of parity data, 12 bytes or symbols of audio data and 4 bytes or symbols of parity data. Hence, 24 bytes, or 12 words, of audio data are contained in each frame, since each word of audio sample data consists of 16 bits. The sub-code part is the EFM data modulated from 8-bit sub-code data, and is arrayed in one block consisting of 98 consecutive frames, with each bit constituting one of eight sub-code channels P to W. It is noted that the sub-code parts for the 1st and 2nd frames are designed as block synchronization patterns S.sub.0 and S.sub.1, respectively, which represent out-of-rule patterns not prescribed in the rule of eight-to-fourteen modulating, while each of the sub-code channels P to W consists of 96 bits for the 3rd to the 98th frames.
The audio data are interleaved prior to being recorded and, for reproduction, are de-interleaved to provide audio data arrayed in the chronological order. In place of these audio data, it is also possible to record so-called CD-ROM data shown for example in FIG. 2 or CD-I data shown in FIG. 3.
Thus, FIG. 2 shows the data construction corresponding to that of audio data consisting of 2352 bytes (=24 bytes.times.98 frames) per block in accordance with the CD standards. In FIG. 2, A, B and C stand for the data constructions for the mode O, mode 1 and mode 2, respectively. In each of these modes, a 12-byte sync part and a 4-byte header part are provided in this order from the leading end of each block consisting of 2352 bytes. The remaining 2336 bytes are all zero data, all user data and 2048 bytes of user data and 288 bytes of subsidiary data, for the mode 0, mode 2 and mode 1, respectively. The 4-byte header part is made up of one byte each for minute, second and block as block addresses and one byte for mode indication. The 288-byte subsidiary data in mode 1 consist of 4 bytes for error detection, 8 bytes for space, 172 bytes for P parity for error correction and 104 bytes for Q parity for error correction. Data scrambling for such error correction is performed within the extent of 2340 bytes inclusive of the header part data.
FIG. 3, or on the other hand, shows the CD-I data construction of 2352 bytes for one block, wherein A and B stand for the data constructions for forms 1 and 2, respectively. In each of these forms, a 12-byte sync part and a 4-byte header are provided in this order from the leading position of each block, as in the case of the CD-ROM described above. The header part is followed by an 8-byte sub-header part within which 2-byte regions each for file, channel, sub-code and data types are provided. The following 2328 bytes are constituted, in form 1, by 2048 bytes as user data, 4 bytes for error detection, 172 bytes for P parity and 104 bytes of Q parity. This form 1 is used for recording letter data, data for binary notation, high compression video data or the like. In form 2, the 2324 bytes following the sub-header part are used as user data and the remaining 4 bytes are reserve data. This form 2 is used for recording audio or video data.
When recording the usual user data in the form of CD-ROM data, sync data, header data or the like need be annexed to the main data in accordance with the above described CD-ROM format. In the case of mode 1, an error detection code (EDC) or an error correction code (ECC) used be generated and annexed as the subsidiary data to the main data. The conventional practice is to prepare such CD-ROM data by a software technique, process the CD-ROM data by a process similar to the process used for the usual digital audio data, formulate a master disc by so-called cutting and to produce the CD-ROM as a medium by a press working process with the aid of a stamper. This process involves additional time and costs, as compared to the case of recording the usual digital audio data for CDs, since the user data must be converted into CD-ROM format data by an additional process.
More, recently a write-once type optical disc is being put into use and it has become highly probable that such write-once optical discs will be used as CD-ROMs. In this case, it takes a lot of time to prepare CD-ROM data with the aid of the software technique as mentioned above. On the other hand, when it is desired that the data format, such as digital audio data for CDs, CD-ROM data or CD-I data, be recorded selectively on the disc, it becomes necessary to prepare the data separately in advance, which involve time-consuming and expensive operations. Thus it is contemplated that the encoding operation up to conversion of the user data into CD-ROM data or CD-I data will be performed by a hardware technique. In this case, it becomes necessary to supply an information for discriminating the data formats to the hardware taking charge of the encoding operation.